The Experts below are selected from a list of 1551 Experts worldwide ranked by ideXlab platform
Di Zhou - One of the best experts on this subject based on the ideXlab platform.
-
microwave dielectric properties of low firing Scheelite related na0 5la0 5 moo4 ceramic
Materials Letters, 2015Co-Authors: Di Zhou, Huidong XieAbstract:Abstract In this paper, the (Na 0.5 La 0.5 )MoO 4 ceramic with a Scheelite Structure was prepared via a solid state reaction method and its microwave dielectric properties were reported for the first time. The (Na 0.5 La 0.5 )MoO 4 ceramic sintered at 740 °C for 2 h possessed a low dielectric permittivity of 11.0, a quality factor ( Qf value) of 25,050 GHz and a temperature coefficient of −59 ppm/ o C at 8.83 GHz. The (Na 0.5 La 0.5 )MoO 4 ceramic is chemically compatible with Ag electrode material at its sintering temperature. It can be a promising microwave dielectric material for low-temperature co-fired ceramics technology (LTCC).
-
raman spectra infrared spectra and microwave dielectric properties of low temperature firing li0 5ln0 5 1 xcax moo4 ln sm and nd solid solution ceramics with Scheelite Structure
Journal of the American Ceramic Society, 2015Co-Authors: Di Zhou, Huidong Xie, Qiuping WangAbstract:In this work, a series of Scheelite solid solution [(Li0.5Ln0.5)1−xCax]MoO4 (Ln = Sm and Nd; x = 0.20, 0.40, 0.60, 0.70, 0.80, 0.85, 0.90) ceramics were prepared by conventional solid-state reaction method. The sintering temperature was lowered to 925°C by (Li0.5Ln0.5)2+ substituting for Ca2+ in the solid solution without any secondary phase. Compared with that of Scheelite CaMoO4 (−57 ppm/°C), the temperature coefficient of resonant frequency (TCF or τf) of the Scheelite solid solution was modified to near zero (about +4.3 ppm/°C) at x = 0.8 with a dielectric constant 11.0 and the quality factor (Q × f value) of 18 695 GHz. The Raman spectra, showed the degree of disordering increased with x value, which resulted in decrease in the permittivities and increase in the Q × f values. The infrared spectra were analyzed using the classical harmonic oscillator model and were extrapolated to the microwave range. The chemical compatibility with silver electrode indicated that the reported series of ceramics were good candidates for the low-temperature cofired ceramic applications.
-
crystal Structure and microwave dielectric behaviors of ultra low temperature fired x ag0 5bi0 5 moo4 1 x bivo4 0 0 x 1 0 solid solution with Scheelite Structure
Inorganic Chemistry, 2014Co-Authors: Di Zhou, Lixia PangAbstract:x(Ag0.5Bi0.5)MoO4–(1 – x)BiVO4 (0.0 ≤ x ≤ 1.0) ceramics were prepared by using the solid-state reaction technique. Ceramics with x 75 and Qf > 9000 GHz, were obtained in ceramics with compositions near x = 0.10. Both the THz data and the infrared spectra were used to study the intrinsic dielectric behavior of the materials at microwave frequencies.
-
phase transition raman spectra infrared spectra band gap and microwave dielectric properties of low temperature firing na0 5xbi1 0 5x moxv1 x o4 solid solution ceramics with Scheelite Structures
Journal of Materials Chemistry, 2011Co-Authors: Hong Wang, Di Zhou, Jing Guo, Xi Yao, Lixia PangAbstract:A Scheelite based Structure that could host the solid solution (Na0.5xBi1−0.5x)(MoxV1−x)O4 (0.0 ≤ x ≤ 1.0) was prepared via the solid state reaction method. All the compositions can be sintered well below a temperature of 800 °C. A structural phase transition occurs from the monoclinic Scheelite Structure to a tetragonal Scheelite Structure at x = 0.10 at room temperature. This structural transition is related to a displacive ferroelastic–paraelastic phase transition. This phase transition was also confirmed by in situhigh temperature XRD and Raman studies, and a room temperature infrared spectra study. The compositions near the phase boundary possessed high dielectric permittivities (>70), and large Qf values (>80 000 GHz) with variable temperature coefficients of frequency and capacitance. For example, a temperature stable dielectric made as a composite with compositions of x = 0.05 and x = 0.10 was designed and co-sintered at 720 °C for 2 h to produce a dielectric with a permittivity of ∼77.3, a Qf value between 8 000 GHz–10 000 GHz, and a temperature coefficient of <±20 ppm/°C at 3.8 GHz over a temperature range of 25–110 °C. This material is a candidate for dielectric resonators and low temperature co-fired ceramics technologies. Near the phase boundary at x = 0.10 in the monoclinic phase region, the samples show strong absorption in the visible light region and we determine a band gap energy of about 2.1 eV, which means that it might also be useful as a visible light irradiation photocatalyst.
-
microwave dielectric ceramics in li2o bi2o3 moo3 system with ultra low sintering temperatures
Journal of the American Ceramic Society, 2010Co-Authors: Hong Wang, Di Zhou, Lixia PangAbstract:A series of compounds in the Li2O–Bi2O3–MoO3 ternary system were investigated with regard to the preparation, phase composition, microwave dielectric properties, and chemical compatibility with silver (Ag) and aluminum (Al) electrodes. All the ceramics in this work have sintering temperatures lower than 750°C. The sintering behaviors and microwave dielectric properties of three single phases Li2MoO4, (Li0.5Bi0.5)MoO4, and Li8Bi2Mo7O28 bulk ceramics, were of particular focus in this investigation. The Li2MoO4 ceramic can be sintered to a high density at 540°C/2 h with a relative permittivity ∼5.5, a Q×f value of 46 000 GHz, and a temperature coefficient of resonant frequency (TCF) of ∼−160 ppm/°C. The (Li0.5Bi0.5)MoO4 ceramic has a Scheelite Structure and the largest relative permittivity of 44.4 among the ceramics studied in this work with a sintering temperature around 560°C, a Q×f value of 3200 GHz, and a large positive TCF of ∼+245 ppm/°C. The Li8Bi2Mo7O28 ceramic could be sintered at 540°C and has a relative permittivity of 13.6, a Q×f value of 8000 GHz, and a small negative TCF value of ∼−59 ppm/°C. From the X-ray diffraction analysis of cofired ceramics, the Li2MoO4 ceramic does not react with either Ag or Al powders. The Li8Bi2Mo7O28 ceramic reacts with Ag but not with Al at its densification temperature. The (Li0.5Bi0.5)MoO4 ceramic was found to strongly react with Ag powder and to a limited extent with Al powders. From this study, the Li2O–Bi2O3–MoO3 ternary system has a number of attractive new materials with low sintering temperatures, high-performing microwave dielectric properties, chemical compatibility with both Ag and Al metal electrodes, nontoxicity, and low-cost constituents. All these materials can be included in the new field of ultra-low-temperature cofiring dielectrics for multilayer applications.
Lixia Pang - One of the best experts on this subject based on the ideXlab platform.
-
crystal Structure and microwave dielectric behaviors of ultra low temperature fired x ag0 5bi0 5 moo4 1 x bivo4 0 0 x 1 0 solid solution with Scheelite Structure
Inorganic Chemistry, 2014Co-Authors: Di Zhou, Lixia PangAbstract:x(Ag0.5Bi0.5)MoO4–(1 – x)BiVO4 (0.0 ≤ x ≤ 1.0) ceramics were prepared by using the solid-state reaction technique. Ceramics with x 75 and Qf > 9000 GHz, were obtained in ceramics with compositions near x = 0.10. Both the THz data and the infrared spectra were used to study the intrinsic dielectric behavior of the materials at microwave frequencies.
-
phase transition raman spectra infrared spectra band gap and microwave dielectric properties of low temperature firing na0 5xbi1 0 5x moxv1 x o4 solid solution ceramics with Scheelite Structures
Journal of Materials Chemistry, 2011Co-Authors: Hong Wang, Di Zhou, Jing Guo, Xi Yao, Lixia PangAbstract:A Scheelite based Structure that could host the solid solution (Na0.5xBi1−0.5x)(MoxV1−x)O4 (0.0 ≤ x ≤ 1.0) was prepared via the solid state reaction method. All the compositions can be sintered well below a temperature of 800 °C. A structural phase transition occurs from the monoclinic Scheelite Structure to a tetragonal Scheelite Structure at x = 0.10 at room temperature. This structural transition is related to a displacive ferroelastic–paraelastic phase transition. This phase transition was also confirmed by in situhigh temperature XRD and Raman studies, and a room temperature infrared spectra study. The compositions near the phase boundary possessed high dielectric permittivities (>70), and large Qf values (>80 000 GHz) with variable temperature coefficients of frequency and capacitance. For example, a temperature stable dielectric made as a composite with compositions of x = 0.05 and x = 0.10 was designed and co-sintered at 720 °C for 2 h to produce a dielectric with a permittivity of ∼77.3, a Qf value between 8 000 GHz–10 000 GHz, and a temperature coefficient of <±20 ppm/°C at 3.8 GHz over a temperature range of 25–110 °C. This material is a candidate for dielectric resonators and low temperature co-fired ceramics technologies. Near the phase boundary at x = 0.10 in the monoclinic phase region, the samples show strong absorption in the visible light region and we determine a band gap energy of about 2.1 eV, which means that it might also be useful as a visible light irradiation photocatalyst.
-
microwave dielectric ceramics in li2o bi2o3 moo3 system with ultra low sintering temperatures
Journal of the American Ceramic Society, 2010Co-Authors: Hong Wang, Di Zhou, Lixia PangAbstract:A series of compounds in the Li2O–Bi2O3–MoO3 ternary system were investigated with regard to the preparation, phase composition, microwave dielectric properties, and chemical compatibility with silver (Ag) and aluminum (Al) electrodes. All the ceramics in this work have sintering temperatures lower than 750°C. The sintering behaviors and microwave dielectric properties of three single phases Li2MoO4, (Li0.5Bi0.5)MoO4, and Li8Bi2Mo7O28 bulk ceramics, were of particular focus in this investigation. The Li2MoO4 ceramic can be sintered to a high density at 540°C/2 h with a relative permittivity ∼5.5, a Q×f value of 46 000 GHz, and a temperature coefficient of resonant frequency (TCF) of ∼−160 ppm/°C. The (Li0.5Bi0.5)MoO4 ceramic has a Scheelite Structure and the largest relative permittivity of 44.4 among the ceramics studied in this work with a sintering temperature around 560°C, a Q×f value of 3200 GHz, and a large positive TCF of ∼+245 ppm/°C. The Li8Bi2Mo7O28 ceramic could be sintered at 540°C and has a relative permittivity of 13.6, a Q×f value of 8000 GHz, and a small negative TCF value of ∼−59 ppm/°C. From the X-ray diffraction analysis of cofired ceramics, the Li2MoO4 ceramic does not react with either Ag or Al powders. The Li8Bi2Mo7O28 ceramic reacts with Ag but not with Al at its densification temperature. The (Li0.5Bi0.5)MoO4 ceramic was found to strongly react with Ag powder and to a limited extent with Al powders. From this study, the Li2O–Bi2O3–MoO3 ternary system has a number of attractive new materials with low sintering temperatures, high-performing microwave dielectric properties, chemical compatibility with both Ag and Al metal electrodes, nontoxicity, and low-cost constituents. All these materials can be included in the new field of ultra-low-temperature cofiring dielectrics for multilayer applications.
Tetyana Milojevic - One of the best experts on this subject based on the ideXlab platform.
-
biotransformation of Scheelite cawo4 by the extreme thermoacidophile metallosphaera sedula tungsten microbial interface
Frontiers in Microbiology, 2019Co-Authors: Amir Blazevic, Mihaela Albu, Stefan Mitsche, Simon K M R Rittmann, Gerlinde Habler, Tetyana MilojevicAbstract:The tungsten-microbial interactions and microbial bioprocessing of tungsten ores, which are still underexplored, are the focus of the current study. Here we show that the biotransformation of tungsten mineral Scheelite performed by the extreme thermoacidophile Metallosphaera sedula leads to the breakage of Scheelite Structure and subsequent tungsten solubilization. Total soluble tungsten is significantly higher in cultures containing M. sedula grown on Scheelite than the abiotic control, indicating active bioleaching. Advanced analytical electron microscopy was used in order to achieve nanoscale resolution ultrastructural studies of M. sedula grown on tungsten bearing Scheelite. In particular, we describe that M. sedula mediated the biotransformation of Scheelite, which was accompanied by the release of tungsten into solution and tungsten biomineralization of the cell surface. Furthermore, we observed intracellular incorporation of redox heterogenous Mn- and Fe-containing nano-clusters. Our results highlight unique metallophilic life in hostile environments extending the knowledge of tungsten biogeochemistry. Based on these findings biohydrometallurgical processing of tungsten ores can be further explored. Importantly, biogenic tungsten carbide-like nanolayers described herein are potential targets for developing nanomaterial biotechnology.
Huidong Xie - One of the best experts on this subject based on the ideXlab platform.
-
microwave dielectric properties of low firing Scheelite related na0 5la0 5 moo4 ceramic
Materials Letters, 2015Co-Authors: Di Zhou, Huidong XieAbstract:Abstract In this paper, the (Na 0.5 La 0.5 )MoO 4 ceramic with a Scheelite Structure was prepared via a solid state reaction method and its microwave dielectric properties were reported for the first time. The (Na 0.5 La 0.5 )MoO 4 ceramic sintered at 740 °C for 2 h possessed a low dielectric permittivity of 11.0, a quality factor ( Qf value) of 25,050 GHz and a temperature coefficient of −59 ppm/ o C at 8.83 GHz. The (Na 0.5 La 0.5 )MoO 4 ceramic is chemically compatible with Ag electrode material at its sintering temperature. It can be a promising microwave dielectric material for low-temperature co-fired ceramics technology (LTCC).
-
raman spectra infrared spectra and microwave dielectric properties of low temperature firing li0 5ln0 5 1 xcax moo4 ln sm and nd solid solution ceramics with Scheelite Structure
Journal of the American Ceramic Society, 2015Co-Authors: Di Zhou, Huidong Xie, Qiuping WangAbstract:In this work, a series of Scheelite solid solution [(Li0.5Ln0.5)1−xCax]MoO4 (Ln = Sm and Nd; x = 0.20, 0.40, 0.60, 0.70, 0.80, 0.85, 0.90) ceramics were prepared by conventional solid-state reaction method. The sintering temperature was lowered to 925°C by (Li0.5Ln0.5)2+ substituting for Ca2+ in the solid solution without any secondary phase. Compared with that of Scheelite CaMoO4 (−57 ppm/°C), the temperature coefficient of resonant frequency (TCF or τf) of the Scheelite solid solution was modified to near zero (about +4.3 ppm/°C) at x = 0.8 with a dielectric constant 11.0 and the quality factor (Q × f value) of 18 695 GHz. The Raman spectra, showed the degree of disordering increased with x value, which resulted in decrease in the permittivities and increase in the Q × f values. The infrared spectra were analyzed using the classical harmonic oscillator model and were extrapolated to the microwave range. The chemical compatibility with silver electrode indicated that the reported series of ceramics were good candidates for the low-temperature cofired ceramic applications.
Leroux Christine - One of the best experts on this subject based on the ideXlab platform.
-
Sr 1/2 Ce 5/14 □ 1/7 WO 4 : a new modulated ternary Scheelite compound
'International Union of Crystallography (IUCr)', 2017Co-Authors: Damascena Dos Passos, Rafael Hernandez, Arab Madjid, Pereira De Souza, Carlson, Leroux ChristineAbstract:International audienceFor the first time, a ternary tetragonal Scheelite Structure tungstate with strontium and cerium cations,(Sr,Ce)WO4, was synthesized. As much as 35 % Ce could be inserted in the Structure, leaving 1/7 of the (Sr,Ce) cation sites vacant. Partial ordering of Sr and Ce, with atomic displacements, were evidenced by high resolution electron microscopy. 2D incommensurate modulations occur in this material, in small domains 20 nm in size. The band gap of this compound is significantly lower than the band gap of SrWO4 and this was related to the distortions of WO4 and (Sr,Ce)O8 polyhedra. The bang gap value of 3.2 eV makes Sr1/2Ce5/14□1/7WO4 a promising candidate for violet luminescence
-
Sr 1/2 Ce 5/14 □ 1/7 WO 4 ; a new modulated ternary Scheelite compound
'International Union of Crystallography (IUCr)', 2017Co-Authors: Damascena Dos Passos, Rafael Hernandez, Arab Madjid, Pereira De Souza, Carlson, Leroux ChristineAbstract:International audienceSynopsis-A new ternary Scheelite tungstate (Sr,Ce)WO 4 phase was synthesized, with a 2D incommensurately modulated Structure linked to partial ordering of Sr, Ce cations and vacancies as was evidenced by high resolution electron microscopy. The bang gap of 3.2 eV makes it a promising violet emitting compound. Abstract-type the Abstract here (Style: IUCr Abstract) For the first time, a ternary tetragonal Scheelite Structure tungstate with strontium and cerium cations,(Sr,Ce)WO 4 , was synthesized. As much as 35 % Ce could be inserted in the Structure, leaving 1/7 of the (Sr,Ce) cation sites vacant. Partial ordering of Sr and Ce, with atomic displacements, were evidenced by high resolution electron microscopy. 2D incommensurate modulations occur in this material, in small domains 20 nm in size. The band gap of this compound is significantly lower than the band gap of SrWO 4 and this was related to the distortions of WO 4 and (Sr,Ce)O 8 polyhedra. The bang gap value of 3.2 eV makes Sr 1/2 Ce 5/14 □ 1/7 WO 4 a promising candidate for violet luminescence
